Utility and method for the application of signal advance amplification to analog waveform or signal detection, acquisition and processing

ABSTRACT

An analog waveform signal detection/data acquisition system that is based on negative group delay for reducing inherent delay in analog waveform or signal detection and acquisition and facilitating earlier than otherwise possible responsive actions to analog waveform data. Signal advance amplification and data conditioning reduces distortion and permits greater temporal advance than previously possible.

CITATION TO PRIORITY APPLICATION

This application claims priority of U.S. Provisional Application, Ser.No. 60/893,983, filed 9 Mar. 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the acquisition and processing ofanalog waveforms or signals, and more specifically to novel applicationsof “Signal Advance” to significantly reduce or eliminate the inherentdelay in analog waveform or signal detection and acquisition.

2. Background Information

Instrumentation relies on the detection, acquisition and processing ofanalog signals or waveforms. The process of acquiring analog signals orwaveforms typically involves detection through an analog signaltransducer, amplification, conversion (including, but not limited to,analog-to-digital conversion) and subsequent signal processing, whichmay include spectral decomposition and typically, signal or data output,for display or control purposes.

Signal detection and processing delays are necessarily inherent in theelectronic systems performing these functions. These delays adverselyimpact the subsequent use of the acquired signal or processed data basedon the acquired signal or waveform, as the physical phenomenonunderlying the generation of the analog signals may continue to vary orsubside during the period that the signal is being detected, acquiredand processed. Any control or intervention necessarily relies on, and insome cases reinforces, or attempts to intervene in underlying eventsthat have transpired, and control, treatment or intervention may be lesseffective.

Because of these analog signal processing delays, there is no reliableway for any response output to control, intervene, treat or respondthrough constructive or destructive interference with the underlyingphenomenon directly. In essence, any such response is to something that,quite literally, is already complete and in the past.

Current instrumentation used in these control, interventional,therapeutic or other related applications typically act to adjustresponse output parameters based on extrapolations made from recentlyacquired data. However, this instrumentation remains unable to reliablyinstigate a true, real-time response, as there is no way to control thetiming of the applied stimulation signal to ensure theappropriately-needed constructive or destructive interference with thephenomenon underlying the generation of the detected analog signal orwaveform. Analog signal or waveform conversion speed, which is criticalto effective response intervention treatment or control in general,could be greatly improved by the early or “pre-” detection of theseanalog signals or by elimination or significant reduction of the analogsignal or waveform detection and processing delays. The application of“Signal Advance” amplification to the detection of analog signals orwaveforms could significantly enhance system response time.

A number of patents and patent applications, as well as, scientificpublications discuss Negative Group Delay (“NGD”).

U.S. Pat. No. 5,291,156, issued to Arntz on Mar. 1, 1994, is entitled“Method and apparatus for imparting positive phase slope to a narrowbandsignal.” It describes a method and apparatus for imparting a positivephase slope (i.e., a negative group delay) to narrowband signals: itadjusts the phases of the various frequency components of a signal in amanner opposite to that of a delay line. The invention also permits theamount of phase slope to be adjusted, electronically, without the needfor electro-mechanical apparatus or the interchange of cables. Theamount of phase slope imparted to the signal can be adjusted by varyingthe gain (or attenuation) of the respective gain control blocks. Assuch, the '156 patent relates to the separation of a signal into twopaths. The first one has a positive delay and thus a negative phaseslope. The second is a parallel path and uses negative group delaycircuitry to impart a positive phase shift, which can compensate for thepositive delay of the first path.

U.S. Patent Application No. 20050127996, published for Jelonnek et al.on Jun. 16, 2005, is entitled “Arrangement for reducing non-lineardistortions in an output signal of an amplifier stage.” This patentapplication describes a system for the reduction of non-linear signaldistortion, which incorporates a negative group delay transmissiondevice to compensate for transmission delay associated with signaldistortion detection in order to generate an error signal that is addedto the original signal to reduce the distortion in the original signalvia a parallel signal pathway for the signal distortion. This patentapplication describes a system for distortion reduction related toamplification based on the “Feed-Forward principle”. It is used toreduce delays associated with the conversation of analog signals todigital signals using a predictive negative delay amplifier stage in theoriginal signal detection/transmission path via the use of a negativegroup delay device in a parallel signal path which is later recombinedwith the original signal propagating through the main signal pathway.

Other references, e.g., U.S. Pat. No. 6,456,950 entitled “Method andapparatus for estimating and digitizing instantaneous frequency andphase of bandpass signals” and U.S. Pat. No. 6,587,064 entitled “Signalprocessor with local signal behavior and predictive capability”, mayincorporate early or “predictive” information about the input signalcharacteristics, but none incorporates a “Signal Advance” amplifier.

Other seemingly-related patents (e.g., U.S. Pat. Nos. 6,466,604,6,222,673, 6,081,379 and 4,853,933) relate to the negative group delayphenomenon applied to lasers and characteristics of varyingconfigurations of radiation generating cavities. However, they have norelationship to the application described in the present invention,which applies the negative group delay phenomenon by using operationalamplifier-based “Signal Advance” amplification to analog signal/waveformdetection and processing in spectral ranges well below those describedthe aforementioned patents.

Also, other seemingly-related patents (e.g., U.S. Pat. Nos. 5,945,861and 6,154,079) relate to the use of a negative delay circuit to offsetdelays in clock signals and prevention of a multi-locking phenomenonrelated to such clock cycles. However, these applications involve clockpulses and not generalized analog signals and act to offset clock signaldelays and not to temporally advance analog signal/waveform detection.Therefore, these groups of patents and similar ones have no relationshipto the application of negative delay amplification to anelectro-physiological interface to enhance signal detection/processingresponse, as in the repent invention.

While these earlier teachings may fulfill their respective, particularobjectives and requirements, no one has to date proposed an analogsignal or waveform detection, acquisition and processing system thatprovides advance or “early detection” of incoming analog waveform peaksand propagates the waveform to the data acquisition system in advance ofthe complete detection of the actual incoming signal or waveform.

SUMMARY OF THE INVENTION

In view of the preceding, it is an object of the present invention toadvance the field of analog signal detection and response.

It is another object of this present invention to provide an analogwaveform signal detection/data acquisition system that incorporates“Signal Advance” amplifier(s) based on the negative group delayphenomenon.

It is another object of this present invention to provide an analogwaveform or signal detection/data acquisition system that cansignificantly improve the performance of instrumentation and devicesused for a variety of control, intervention, suppression, reinforcement,enhancement, alarm, treatment or responsive processes that relate todetected analog waveforms or signals.

It is another object of this present invention to provide an analogwaveform or signal detection/data acquisition system that can provide areliable way to investigate or perform reinforcement (negative orpositive) between an applied stimulation response or signal and thephysiological or other processes underlying the generation of the analogsignal or waveform being temporally advanced.

It is another object of this present invention to provide an analogwaveform or signal detection/data acquisition system that can reliablyinstigate a true, real-time response by controlling the timing of theapplied stimulation signal or other response output to insure real-timeconstructive or destructive interference with the actual processunderlying the generation of the detected analog waveform or signalincluding, but not limited to, actual physiological responses.

It is another object of this present invention to provide an analogwaveform signal detection/data acquisition system that can significantlyenhance a range of electrophysiological and neuro-therapeuticapplications, such as EMG, EKG, myelogram, EEG-controlled stimulation,neurofeedback (active or passive) and other neuro-therapy.

It is another object of this present invention to provide an analogwaveform signal detection/data acquisition system that can provide newresearch tools to investigate mechanisms underlying analog signal orwaveform generation, including a wide range of physiological andelectrophysiological mechanisms.

It is another object of this present invention to provide an analogwaveform signal detection/data acquisition system that can enhance theresponse time and performance of brain-computer interfaces.

It is another object of this present invention to provide an analogwaveform signal detection/data acquisition system that can generatesignificant and useable temporal signal advance for analog signals orwaveforms with spectral content typical of electrophysiological signalsor waveforms.

It is another object of this present invention to provide an analogwaveform signal detection/data acquisition system that can generatesignificant and useable temporal signal advance for analog signals orwaveforms for a wide range of transduced analog signals or waveformsrepresenting a physical measurement for interventional or controlpurposes.

It is another object of this present invention to provide an analogwaveform signal detection/data acquisition system that can generatesignificant and useable temporal signal advance for analog signals orwaveforms for a wide range of analog signals or waveforms to controlsystem(s) that generate analog signals which can be applied to variousprocesses.

It is another object of this present invention to provide an analogwaveform signal detection/data acquisition system that can generatesignificant and useable temporal signal advance for analog signals inwhich a change in signal or waveform amplitude represents a binary statetransition from either a “true” to “false” or “false” to “true” state.

In satisfaction of these and related object, the present inventionteaches a unique implementation and use of negative group delayband-pass amplification. Its preferred embodiment is applied to analogwaveform signal detection, acquisition and processing. The analogwaveform signal detection/data acquisition system incorporates negativegroup delay band-pass amplification in analog waveform signal detection,acquisition and processing. The result is a significant and useablesignal advance for analog waveform signals, especially those with aspectral content in the low end of the spectrum. This useable signaladvance will at least reduce if not eliminate signal processing delaysand thus, has broad control system, scientific, medical and researchapplications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 generally describes the process of acquiring analog signals orwaveforms, which typically involves detection through an analog signaltransducer, amplification, conversion (including, but not limited to,analog-to-digital conversion) and subsequent signal processing. It mayinclude spectral decomposition and typically, signal or data output, fordisplay or control purposes.

FIG. 2 generally describes the application of “Signal Advance”amplification to the detection of analog signals or waveforms and thussignificantly enhances the system response time.

FIG. 3 depicts the relationship of the output to the input of a simpleelectronic circuit using a Gaussian pulse and sinusoid as inputwaveforms in which the output waveform peaks precede those of theinputs.

FIG. 4 illustrates the simplest form of such an operational amplifiercircuit that exhibits this counter-intuitive response consists of asingle stage operational amplifier with a passive linear feedback loopcomprised of resistive, capacitive and/or inductive components.

FIG. 5 illustrates group velocity, i.e., the speed of a pulse/waveform,

FIG. 6 illustrates a simple circuit consisting of an operationalamplifier, two resisters and two capacitors, which exhibits negativegroup delay properties over a specific spectral band (frequencies wellbelow the amplifier's characteristic frequency).

FIG. 7 illustrates the “Signal Advance” amplifier circuit, whichincludes inductive, resistive and capacitive components.

FIG. 8 illustrates a circuit similar to the previous circuit of FIG. 7and is cascaded with each stage exhibiting different transfer functiondue to the use of different resistor, capacitor and inductor values.With specific component selection, this multi-stage “Signal Advance”amplifier exhibits a relatively constant advance over a wider spectralrange.

FIG. 9 depicts Gain, Phase and Group Delay characteristics of a signaladvance amplifier in which the negative group delay is relativelyconstant over a specific spectral range. The top graph depicts the gainof the amplifier relative to frequency. Note that the gain is relativelyconstant up to 200 Hz, a spectral band which is less than, and adjacentto the lower of the two characteristic frequencies of the amplifiercircuit. The middle graph (phase vs. frequency) indicates both apositive and relatively linear phase response up to approximately 200Hz. The third graph depicts the group delay relative to frequency. Groupdelay is defined as the negative of the rate of change of phase relativeto frequency and is expressed mathematically as: [τ(ω)=−δψ(ω)/δω] (inthe units of time).

FIG. 10 illustrates how the duration of the waveform advance can beincreased (in a limited fashion due to concomitant, but acceptable,signal distortion) by cascading multiple negative group delay amplifierstages over a limited spectral range.

FIG. 11 illustrates parallel arrays of narrow “Signal Advance”amplifiers, in which some of the bands the “Signal Advance” amplifiersare cascaded. This parallel array of amplifiers can be configured togenerate a more linear input-output response, which in turn can yield atemporal advance of signals over particular spectral ranges of interest.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Modern instrumentation relies on detection, acquisition and processingof analog signals. The performance of the technology used to acquire andprocess these signals has improved drastically over the last twentyyears, but despite these improvements, current systems necessarily haveinherent delays, albeit slight (some on the order of microseconds),between the actual generation of analog waveforms to be detected and theability to react to the acquired data.

In recent years, a negative group delay (NGD) phenomenon has beendemonstrated in relatively simple electronic circuits, and shown totemporally advance Gaussian pulses, sinusoidal waveforms and complexanalog waveforms comprised of multiple superposed sinusoidal components.FIG. 3 depicts the relationship of the output to the input of just sucha circuit using a Gaussian pulse and sinusoid as input waveforms inwhich the output waveform peaks precede those of the inputs. Note thedistortion of the output waveform relative to the input in which theoutput is slightly “skewed” to the left indicating the introduction ofhigher frequency elements. Over a limited spectral band, the distortionis negligible and linear, facilitating algorithmic removal of distortiondigitally for applications in which the advanced analog signal mustfaithfully reflect the characteristics input signal.

The simplest form of such an operational amplifier circuit that exhibitsthis counter-intuitive response consists of a single stage operationalamplifier with a passive linear feedback loop comprised of resistive,capacitive and/or inductive components.

Typically, an electromagnetic signal or waveform passing through apassive linear circuit will exhibit a positive delay. However, high-gainoperational amplifiers act to minimize differences between signalsapplied to the inverting (−) and non-inverting (+) inputs. In order tosatisfy this functional requirement, the operational amplifier suppliesa signal with a negative group delay at its output to offset thepositive group delay from the passive linear circuit applied to theinverting (−) input. Thus, the negative feedback circuit generates anoutput pulse whose peak exits the output of the circuit before the peakof the input pulse arrives at the input.

Operational amplifier configurations, which invert transfer functions,are not without precedent. Negative-impedance converters function tocause a resistive load to behave like a negative load. A gyrator circuitinverts impedance such that capacitance behaves like inductance.

At first glance, the behaviour of these circuits appears to contradictthe laws of physics as the results suggest that the advanced signalpropagation is super-luminal. However, electromagnetic propagation isactually characterized by five different velocities: front velocity(speed of an abrupt signal discontinuity, e.g., a signal suddenly turnedon or off); group velocity (speed of a pulse/waveform), phase velocity,velocity of energy transport and, finally, a presumed signal velocity.While the front velocity cannot exceed the speed of light, “ . . . thegroup velocity . . . can be greater than the velocity of light c, can beinfinite and even negative!” [Brillouin L, Wave Propagation and GroupVelocity, Academic Press, NY, 1960]. As such, the detection of anelectromagnetic pulse or wave-form at the output can precede detectionat the input. During the time interval between the signal front and thedetection of group waveform, electromagnetic energy begins to propagatethrough the circuit. However, these initial perturbations are notdetectable until the oscillations achieve sufficient magnitude. Thereexists, however, sufficient information in the early portion of anyanalog waveform to reproduce a temporally advanced waveform using ahigh-gain operational amplifier.

Thus, the output of an electromagnetic waveform (the group velocity) canbe advanced relative to the input—but it cannot exceed the frontvelocity and thus establishes a theoretical upper limit for a groupvelocity advance. Further, the question of “superluminality” has beenaddressed in a number of experiments in which the input signal wasdiscontinued abruptly resulting in a simultaneous (not advanced)discontinuity or signal abruption in the “advanced” output waveform,which demonstrates the causal relationship between the input andadvanced output waveforms.

A simple circuit consisting of an operational amplifier, two resistersand two capacitors, which exhibits negative group delay properties overa specific spectral band (frequencies well below the amplifier'scharacteristic frequency), is shown in FIG. 6. For this circuit, thetransfer function (Tω) defined as the output signal/input signal isdefined as follows:

${T(\omega)} = {{\overset{\sim}{V}{{out}/\overset{\sim}{V}}\; i\; n} = {\left( {1 + {Z_{R}/Z_{c}}} \right) = {1 + \frac{\; \omega \; T}{\left( {1 + {\; \omega \; {aT}}} \right)\left( {1 + {\; \omega \; {bT}}} \right)}}}}$

where T=CR, a=C′/C, b=R′/R

The “Signal Advance” amplifier circuit shown in FIG. 7 includesinductive as well as resistive and capacitive components. Circuitanalysis yields the following a transfer function:

${T(\omega)} = {1 + {\frac{1}{R^{\prime}} \cdot \frac{1}{\left( {R - {\; \omega \; L}} \right)^{- 1} - {\; \omega \; C}}}}$

A circuit similar to the previous circuit was cascaded (FIG. 8) witheach stage exhibiting different transfer function due to the use ofdifferent resistor, capacitor and inductor values. By varying the thesecomponents values, the multi-stage “Signal Advance” amplifier canexhibit a relatively constant advance of the spectral range of interestfor a particular application. The transfer function is expressed as:

${T(\omega)} = \left. \left\lbrack {1 + {\left( \frac{1}{R\; 2} \right)\left( \frac{1}{\left( {{r\; 1} - {\; \omega \; L\; 1}} \right)^{- 1} - {\; {wC}\; 1}} \right)}} \right\rbrack \middle| {\quad\left\lbrack {1 + {\left( \frac{1}{R\; 4} \right){X\left( \frac{1}{\left( {{R\; 3} - {\; \omega \; L\; 2}} \right)^{- 1} - {\; {wC}\; 2}} \right)}}} \right\rbrack} \right.$

The phase associated with these transfer functions is given by:

ψ(ω)=arg[T(ω)

Circuit analyses for the exemplar “Signal Advance” amplifier circuitsdescribed above reveal spectral bands which exhibit negative group delayfor a frequency band adjacent to the characteristic or resonantfrequency of the circuit. It is within this negative delay spectral bandthat the circuit(s) generates an analog signal advance.

FIG. 9 depicts Gain, Phase and Group Delay characteristics of a signaladvance amplifier in which the negative group delay is relativelyconstant over a specific spectral range. The top graph depicts the gainof the amplifier relative to frequency. The gain is relatively constantup to 200 Hz, a spectral band which is less than, and adjacent to thelower of the two characteristic frequencies of the amplifier circuit.The middle graph (phase vs. frequency) indicates both a positive andrelatively linear phase response up to approximately 200 Hz. The thirdgraph depicts the group delay relative to frequency. Group delay isdefined as the negative of the rate of change of phase relative tofrequency and is expressed mathematically as: [τ(ω)=−δψ(ω)/δω] (in theunits of time). Again, the slope of the phase delay is positive andrelatively linear; thus, its derivative is negative and constant in thespectral range less than 200 Hz.

Based on the detailed analyses of the exemplar negative delay circuitsdetailed above, the amount of negative delay, or signal advance, whichcan be achieved, is indirectly related to the spectral content orfrequency of the analog waveform to which it is applied, i.e., a largernegative delay or signal advance is possible for lower frequencysignals.

Note that the use of the inductive component in the negative group delaycircuits facilitates signal advance for a complex analog signal over awider spectral band. As described previously, larger analog signaladvances are indirectly proportional to the spectral content of theanalog waveform. To achieve a lower characteristic or resonant frequencyin a “Signal Advance” amplifier circuit may require both a largecapacitance and inductance as the resonant frequency (ω_(r)) isapproximated by:

$\omega_{r} \approx {1/{\sqrt{LC}.}}$

Inductors are typically measured in units of milli-henries (mH) orlower. Thus, a gyrator may be used to simulate large inductance values(measured in Henries (H)).

For a number of applications and, in particular, biomedicalinterventional applications such as electrophysiology, the temporallyadvanced output may need to be a high fidelity representation of theoriginal input waveform. In these applications, the analog waveformsbeing advanced are typically in the lower frequency range (hundreds ofHertz). Thus, compensation for the inherent signal distortion can beaccomplished through the use of digital signal processors which operateat conversion rates that are negligible with respect to the duration ofwaveform advance achieved. A number of analog-to-digital (A-D)converters and digital signal processors, which can be used to performdigital filtering and signal reconstruction, have response times rangingfrom just under 100 to over 1,000 times less than the expected waveformadvance.

The duration of the waveform advance can be increased (in a limitedfashion due to concomitant, but acceptable, signal distortion) bycascading multiple negative group delay amplifier stages over a limitedspectral range (FIG. 10). By cascading multiple “Signal Advance”Amplifier stages, a waveform advance could exceed the input pulse width,but the maximum advance may be limited to a few pulse rise-times due tothe increase in signal distortion in each stage and the theoreticalfront velocity limit.

As discussed previously, digital filtering and signal reconstruction canbe applied to reduce or eliminate the waveform or signal distortion in afraction of the duration of the temporal waveform advance achieved.Reduction or elimination of higher frequency distortion resulting from“Signal Advance” amplification, which approaches the characteristic orresonant frequency of the circuit, is particularly useful whensuccessive amplifier stages are cascaded to achieve increased durationof the temporal waveform or signal advance

Parallel arrays of narrow “Signal Advance” amplifiers, in which some ofthe bands the “Signal Advance” amplifiers are cascaded (FIG. 11), can beconfigured to generate a more linear input-output response. Thisprovides a mechanism to achieve a temporal advance of signals orwaveforms over particular spectral ranges of interest as narrow spectralbands can be tuned to detect specific aspects of the incoming analogsignal or waveform through the use of just such a cascade arrangement.

As such, for a wide range of instrumentation used in analog signal orwaveform detection, acquisition and processing, an approach utilizing“Signal Advance” amplification holds the promise of significantlyenhancing a range of control and biomedical applications.

A primary consideration in practical application of “Signal Advance”amplification to analog signal detection, acquisition and processing isto achieve a sufficient signal advance to allow for a usable response.Therefore, design of a practical “Signal Advance” amplifier necessarilybegins with a detailed analysis of the analog waveform to be advanced inorder to determine the waveform characteristics for which circuitry mustbe designed. The amplifier design must take in account waveformcharacteristics which include the frequency range, pulse widths (ordurations) comprising the signal, pulse shape, etc.

The second consideration is, after determining the signal advance whichcan be achieved, is to determine the potential to produce a useableresponse based on the duration of the temporal advance obtained. It maybe necessary to cascade multiple stages or to detect different aspectsof the analog waveform using parallel “Signal Advance” paths. It is theability to provide a useable response given the availability of advancedsignal or waveform detection that is the key to practical application ofthis technology.

For some potential applications of the present invention, signaldistortion is of little or no consequence. One example is the detectionof an analog pulse in which the difference in amplitude, or simply theexistence of a pulse, represents a change in a binary state, a thresholdcondition, or other true/false transition. In ECG/EKG(Electro-Cardiograph) waveform detection, a slightly distorted PQRSTwaveform may still be acceptable for the detection of abnormal wavepatterns as long as the signals distortions resulting from “SignalAdvance” amplification are consistent. Other applications, such asneurofeedback, may require or benefit from the removal of, orcompensation for, the signal distortion, as it is the spectral contentthat may be important to the therapeutic application.

In order to develop a mechanism for compensating the distortion whichresults from “Signal Advance” amplification, the resultant distortionsarising in the advance analog signals or waveforms must be characterizedfor the particular spectral range and at a resolution appropriate forthe analog waveforms being detected. In order to generate data that canbe used to devise methodologies and algorithms for reconstituting thespectral content of the original analog input signal or waveform, signalgeneration and data acquisition systems, which provide synchronized highsample-rate and wide bandwidth simultaneous data sampling and signalgeneration capacity are used to generate high fidelity analog inputsignal and acquire the temporally advanced analog output signals orwaveforms. Spectral decomposition of both the input and output signalsare obtained by applying fast Fourier Transform (FFT) analyses to theinput and output signals from each “Signal Advance” amplifier stage. Thecomparison of the spectral content of the respective signals providesdata to characterize and digitally reconstitute the spectral content ofthe original analog input waveform.

As the distortion is minimal and consistent across a narrow band,empirically-obtained data, as described above, can be used tocharacterize the distortion and devise methods for subsequent removal ofthe distortion digitally for a particular application. For example, asimple “look-up” table could be incorporated into embedded hardware thatreplaces the spectrally decomposed components of the advanced signals orwaveforms with the equivalent amplitude and frequency data for theoriginal input signal.

Although the invention has been described with reference to specificembodiments, this description is not meant to be construed in a limitedsense. Various modifications of the disclosed embodiments, as well asalternative embodiments of the inventions will become apparent topersons skilled in the art upon the reference to the description of theinvention. It is, therefore, contemplated that the appended claims willcover such modifications that fall within the scope of the invention.

1. A method for temporally advancing the detection and characterizationof analog data for temporally advanced responsive actions to such analogdata comprising the steps of: selecting analog data detection means,said analog data detection means being interfaced with first negativegroup delay circuit means having first NGD signal output means forproducing first temporally advanced raw indicia of analog data receivedby said analog data detection means, said first NGD signal output meansbeing interfaced with first signal advance amplifier means forproducing, at a first signal advance amplifier output, first correctedindicia that more accurately represents said analog data detected bysaid analog data detection means than said first temporally advanced rawindicia; applying said data input means to a source of analog data;effecting a responsive action to said first corrected indicia producedby said first signal advance amplifier means.
 2. A method for temporallyadvancing the detection and characterization of analog data fortemporally advanced responsive actions to such analog data comprisingthe steps of: selecting analog data detection means, said analog datadetection means being interfaced with first negative group delay circuitmeans having first NGD signal output means for producing firsttemporally advanced raw indicia of analog data received by said analogdata detection means, said first NGD signal output means beinginterfaced with first signal advance amplifier means for producing, at afirst signal advance amplifier output, first corrected indicia that moreaccurately represents said analog data detected by said analog datadetection means than said first temporally advanced raw indicia; saidfirst signal advance amplifier output being interfaced with a secondnegative group delay circuit means having second NGD signal output meansfor producing second temporally advanced raw indicia of analog datareceived by said analog data detection means and first processed by saidfirst negative group delay circuit means and said first signal advanceamplifier means, said second NGD signal output means being interfacedwith second signal advance amplifier means for producing, at a secondsignal advance amplifier output, second corrected indicia that moreaccurately represents said analog data detected by said analog datadetection means than said second temporally advanced raw indicia;applying said data input means to a source of analog data; effecting aresponsive action to said first corrected indicia produced by saidsecond signal advance amplifier means.
 3. A method for temporallyadvancing the detection and characterization of analog data fortemporally advanced responsive actions to such analog data, where N is apositive integer, comprising the steps of: selecting analog datadetection means, said analog data detection means being interfaced,directly or indirectly, with an N negative group delay circuit meanshaving an N NGD signal output means for producing an N temporallyadvanced raw indicia of analog data received by said analog datadetection means, said N NGD signal output means being interfaced with anN signal advance amplifier means for producing, at a N signal advanceamplifier output, an N corrected indicia that more accurately representssaid analog data detected by said analog data detection means than saidN temporally advanced raw indicia; said N signal advance amplifieroutput being interfaced with a N+1 negative group delay circuit meanshaving a N+1 NGD signal output means for producing a N+1 temporallyadvanced raw indicia of analog data received by said analog datadetection means and first processed by said N negative group delaycircuit means and said N signal advance amplifier means, said N+1 NGDsignal output means being interfaced with an N+1 signal advanceamplifier means for producing, at an N+1 signal advance amplifieroutput, N+1 corrected indicia that more accurately represents saidanalog data detected by said analog data detection means than said N+1temporally advanced raw indicia; applying said data input means to asource of analog data; effecting a responsive action to said N+1corrected indicia produced by said N+1 signal advance amplifier means.4. An apparatus for temporally advancing the detection andcharacterization of analog data for temporally advanced responsiveactions to such analog data comprising: analog data detection means,said analog data detection means being interfaced with first negativegroup delay circuit means having first NGD signal output means forproducing first temporally advanced raw indicia of analog data receivedby said analog data detection means, said first NGD signal output meansbeing interfaced with first signal advance amplifier means forproducing, at a first signal advance amplifier output, first correctedindicia that more accurately represents said analog data detected bysaid analog data detection means than said first temporally advanced rawindicia.
 5. An apparatus for temporally advancing the detection andcharacterization of analog data for temporally advanced responsiveactions to such analog data, where N is a positive integer, comprising:analog data detection means, said analog data detection means beinginterfaced, directly or indirectly, with an N negative group delaycircuit means having an N NGD signal output means for producing an Ntemporally advanced raw indicia of analog data received by said analogdata detection means, said N NGD signal output means being interfacedwith an N signal advance amplifier means for producing, at a N signaladvance amplifier output, an N corrected indicia that more accuratelyrepresents said analog data detected by said analog data detection meansthan said N temporally advanced raw indicia; said N signal advanceamplifier output being interfaced with a N+1 negative group delaycircuit means having a N+1 NGD signal output means for producing a N+1temporally advanced raw indicia of analog data received by said analogdata detection means and first processed by said N negative group delaycircuit means and said N signal advance amplifier means, said N+1 NGDsignal output means being interfaced with an N+1 signal advanceamplifier means for producing, at an N+1 signal advance amplifieroutput, N+1 corrected indicia that more accurately represents saidanalog data detected by said analog data detection means than said N+1temporally advanced raw indicia.
 6. The method of claim 1 wherein saidanalog data detection means is a medical monitoring device for detectingand transmitting data indicative of electromagnetic waves produced byorgans and systems of the human body.
 7. The method of claim 6 whereinsaid medical monitoring device is an EKG monitor.
 8. The method of claim6 wherein said medical monitoring device is an EEG monitor,
 9. Themethod of claim 2 wherein said analog data detection means is a medicalmonitoring device for detecting and transmitting data indicative ofelectromagnetic waves produced by organs and systems of the human body.10. The method of claim 9 wherein said medical monitoring device is anEKG monitor.
 11. The method of claim 9 wherein said medical monitoringdevice is an EEG monitor,
 12. The method of claim 3 wherein said analogdata detection means is a medical monitoring device for detecting andtransmitting data indicative of electromagnetic waves produced by organsand systems of the human body.
 13. The method of claim 12 wherein saidmedical monitoring device is an EKG monitor.
 14. The method of claim 12wherein said medical monitoring device is an EEG monitor,
 15. Theapparatus of claim 4 wherein said analog data detection means is amedical monitoring device for detecting and transmitting data indicativeof electromagnetic waves produced by organs and systems of the humanbody.
 16. The method of claim 15 wherein said medical monitoring deviceis an EKG monitor.
 17. The method of claim 15 wherein said medicalmonitoring device is an EEG monitor,
 18. The apparatus of claim 5wherein said analog data detection means is a medical monitoring devicefor detecting and transmitting data indicative of electromagnetic wavesproduced by organs and systems of the human body.
 19. The method ofclaim 18 wherein said medical monitoring device is an EKG monitor. 20.The method of claim 18 wherein said medical monitoring device is an EEGmonitor,
 21. An apparatus for temporally advancing the detection andcharacterization of analog data for temporally advanced responsiveactions to such analog data comprising: analog data detection means,said analog data detection means being interfaced with first negativegroup delay circuit means having first NGD signal output means forproducing first temporally advanced raw indicia of analog data receivedby said analog data detection means, said first NGD signal output meansbeing interfaced with first digital filtering and signal reconstructionmeans for producing, at a first digital filtering and signalreconstruction means output, first corrected indicia that moreaccurately represents said analog data detected by said analog datadetection means than said first temporally advanced raw indicia.
 22. Anapparatus for temporally advancing the detection and characterization ofanalog data for temporally advanced responsive actions to such analogdata, where N is a positive integer, comprising: analog data detectionmeans, said analog data detection means being interfaced, directly orindirectly, with an N negative group delay circuit means having an N NGDsignal output means for producing an N temporally advanced raw indiciaof analog data received by said analog data detection means, said N NGDsignal output means being interfaced with an N digital filtering andsignal reconstruction means for producing, at a N digital filtering andsignal reconstruction means output, an N corrected indicia that moreaccurately represents said analog data detected by said analog datadetection means than said N temporally advanced raw indicia; said Nsignal advance amplifier output being interfaced with a N+1 negativegroup delay circuit means having a N+1 NGD signal output means forproducing a N+1 temporally advanced raw indicia of analog data receivedby said analog data detection means and first processed by said Nnegative group delay circuit means and said N digital filtering andsignal reconstruction means, said N+1 NGD signal output means beinginterfaced with an N+1 digital filtering and signal reconstruction meansfor producing, at an N+1 digital filtering and signal reconstructionoutput, N+1 corrected indicia that more accurately represents saidanalog data detected by said analog data detection means than said N+1temporally advanced raw indicia.
 23. A method for temporally advancingthe detection and characterization of analog data for temporallyadvanced responsive actions to such analog data, where N is a positiveinteger, comprising the steps of: selecting analog data detection means,said analog data detection means being interfaced, directly orindirectly, with an N negative group delay circuit means having an N NGDsignal output means for producing an N temporally advanced raw indiciaof analog data received by said analog data detection means, said N NGDsignal output means being interfaced with an N digital filtering andsignal reconstruction means for producing, at a N digital filtering andsignal reconstruction means output, an N corrected indicia that moreaccurately represents said analog data detected by said analog datadetection means than said N temporally advanced raw indicia; said Nsignal advance amplifier output being interfaced with a N+1 negativegroup delay circuit means having a N+1 NGD signal output means forproducing a N+1 temporally advanced raw indicia of analog data receivedby said analog data detection means and first processed by said Nnegative group delay circuit means and said N digital filtering andsignal reconstruction means, said N+1 NGD signal output means beinginterfaced with an N+1 digital filtering and signal reconstruction meansfor producing, at an N+1 digital filtering and signal reconstructionoutput, N+1 corrected indicia that more accurately represents saidanalog data detected by said analog data detection means than said N+1temporally advanced raw indicia. applying said data input means to asource of analog data; effecting a responsive action to said N+1corrected indicia produced by said N+1 digital filtering and signalreconstruction means.